Magnetic field-induced topological domains in twisted nodal superconductors

Topological phases have been predicted to emerge in twisted bilayers of nodal superconductors with time-reversal symmetry broken either spontaneously or by applying current. Here we study the quasiparticle spectrum in the presence of an in-plane magnetic field generating a Josephson vortex lattice.

At nonzero twist angle we find that states forming low-energy bands are localized in the “cores” of the vortices, where interlayer current vanishes, and have chiral motion along the field direction. The low-energy bands are separated from the rest by an energy gap that decreases with decreasing average magnetic field. These results can be attributed to the formation of topological domains with alternating Chern number. Finally, we discuss how these results can be used to probe topology of twisted nodal superconductors using scanning tunneling microscopy experiments in magnetic field.